Proprietary resin allows addition and subtraction using 3D printing methods

Additive manufacturing (3D printing) is typically a one-way street. Digital light processing (DLP) printers project a structured pattern onto a layer of liquid resin, which hardens and solidifies. This builds the object layer by layer. But if the print isn’t quite right, there’s no easy way to fix it later and it usually ends up in the trash.

New resin enables reversible 3D printing

In a new study published in Advanced Materials Technologies, researchers at Lawrence Livermore National Laboratory (LLNL) have developed a hybrid additive and subtractive manufacturing system using a proprietary resin that enhances traditional 3D printing by introducing dual-wavelength operation. Under blue light, the resin hardens and hardens. Under UV light, it decomposes back into a liquid. The hybrid printing system enables corrective manufacturing, increases print resolution, and allows parts to be upcycled and recycled.

“Imagine a company needs a part to fit into a particular machine, but it’s a prototype and they don’t really know what they want,” said LLNL scientist and author Benjamin Alameda. “Theoretically, you could print with our resin, and if there was a defect or something you wanted to change, you wouldn’t have to print a completely new part. You could just apply a different wavelength and modify the existing part. This is convenient and reduces waste.”

As an example, the researchers printed a fluidic device with two separate channels. Using the decomposition reaction of the resin, we were able to connect the channels after printing.

“We did it this way on purpose. But if this really fails to connect the channels, we’ll have to redo the entire print,” said LLNL scientist and author Johanna Schwartz. “We only had to make some very simple fixes after the fact, and now we can use it again.”

Commercialization of resin and technical details

This patented resin technology is available for commercialization through LLNL’s Innovation and Partnership Office (IPO). This allows all light-based printing systems to create more complex and detailed parts at high resolution, smooth surfaces and correct errors, and add and remove temporary support structures. Manufactured using LLNL’s unique equipment, capabilities and expertise, this technology can be licensed by advanced manufacturing companies and used with existing 3D printers to save time and material costs by enabling editable and recyclable 3D printing.

Resin is the key to the success of this dual-function printing. The authors optimized each component of its chemical properties. The blue light causes molecules within the resin to bond together to form a cross-linked network. This is a standard technology in 3D printing. In a new twist, ultraviolet light creates acid within the resin. This molecule is specially tailored to react with acids and break down into a liquid.

The challenge was to find a balance between stability and degradability. The team designed the resin to harden and break down quickly, but not so quickly that it would break down on its own. They pointed out that standard coatings can prevent component failure from the sun’s natural UV rays.

Future direction of adaptive manufacturing

Going forward, scientists will further extend the capabilities of this hybrid manufacturing by integrating on-machine measurement and feedback control to automatically and autonomously correct printing errors on the fly.

“Once we know there are printing errors, we can adaptively change the projection image to correct those errors on the fly, enabling true adaptive manufacturing. Besides DLP printing, we also plan to move this method to volumetric additive and subtractive manufacturing, which shines light onto a rotating vial of resin to produce 3D parts one at a time,” said author and LLNL scientist Liliana Donpin Terrell Perez.

This project was led by Liliana Dongping Terrel-Perez. In addition to Alameda and Schwartz, team members include Holden Howard, Martin De Beer and Maj Yassa.